bpo-46406: Faster single digit int division. (#30626)

* bpo-46406: Faster single digit int division.

This expresses the algorithm in a more basic manner resulting in better
instruction generation by todays compilers.

See https://mail.python.org/archives/list/python-dev@python.org/thread/ZICIMX5VFCX4IOFH5NUPVHCUJCQ4Q7QM/#NEUNFZU3TQU4CPTYZNF3WCN7DOJBBTK5